如何在将POD结构作为变量传递时初始化它？

Question

For instance i have a RECT and a some sub that has a RECT as a parameter

RECT wr = {0, 0, somevar1, somevar2};
someSub(wr);

Since i dont need the RECT anywhere else is there a way to initialize it as i send it to the sub? Something like

someSub(RECT {0, 0, somevar1, somevar2}); <- doesnt work :(

oh ya using vs2010 to compile

Answer 1

What I've did in the past is to create a substruct with a constructor:

struct Rect : RECT
{
    Rect(long l, long t, long r, long b)
    {
        left   = l;
        top    = t;
        right  = r;
        bottom = b;
    }
};

someSub(Rect(a, b, c, d));

The Rect itself is not a POD, because it has a constructor, but it will be spliced or downcasted into a RECT (or RECT& ) on passing to the function.

Naturally, if you look at it, it is no different than creating a function:

RECT Rect(long l, long t, long r, long b)
{
    RECT r = {l, t, r, b};
    return r;
}

It even has the same syntax! But the constructor thing feels to me somewhat better.

Answer 2

In C++11, you can inline the struct in the call:

func({0, 0, somevar1, somevar2});

In older versions of C/C++, you can create a helper function that initializes the structure and returns the result:

inline RECT new_RECT(int a, int b, int c, int d)
{
    RECT ret = {a, b, c, d};
    return ret;
}

Then you can call:

func(new_RECT(a, b, c, d));

and the struct creation should be inlined by the compiler.